Abstract: Objective To explore the effect of doxorubicin (DOX) combined with a Heat shock protein 90 targeted heptapeptide - LPLTPLP (P7) in the acute myeloid leukemia cell line NB4 in vitro. Methods Following treatment with P7, DOX, or P7 combined with DOX fin NB4 cells for 48 h, cell viability was assessed by CCK-8 assay and analysis with the isobologram method；Flow cytometry was carried out to quantify apoptotic cells；The expression and cleavage level of PARP protein were investigated by Western blot analysis. Results P7 synergized with DOX for inhibiting cell viability. The apoptotic rate of combination of P7 and DOX was approximately equal to the sum of P7 and DOX apoptotic rate. The protein expression of PARP was significantly decreased while that of cleaved PARP was significantly increased with the treatment of P7 or/and DOX. Conclusions Combination of P7 and DOX exhibits synergistic effects on NB4 cells by increasing apoptosis rate, the mechanism of which may be associated with the activation of apoptosis-related protein PARP.

Key words: Acute myeloid leukemia, Apoptosis, Doxorubicin, Heptapeptide, synergy